The combination of the Internet Protocol (IP) and multi-protocol label switching (MPLS) Fast Reroute (FRR) technologies address the problem with the long time it takes routing protocols to converge across networks. The problem is addressed by providing backup paths in the forwarding plane, which are used when network failures occur, while the routing protocol is reconverging. These technologies are important due to the increased use of IP transport for real time services such as video, voice and TV and the increasing number of web services which all are expected to work without disruption.
The standard approach used in existing technologies, such as open shortest path first (OSPF), intermediate system intermediate system (ISIS), label distribution protocol (LDP) loop free alternative (LFA), maximally redundant trees (MRT), border gateway protocol (BGP) FRR, is to gather network information using a routing/signaling protocol and based on that information compute the backup paths necessary to prepare for failures of adjacent links or nodes, and then to pre-provision the forwarding plane with those back-up paths. The forwarding plane is then able to react to a failure event and switch from a primary path to a pre-provisioned back-up path without waiting for the routing protocol to gather updated network information and reconverge. Instead each of the network nodes switch from the primary path to the backup path and continue to utilize the backup path until the completion of the reconvergence of the network resulting in the calculation of new primary paths.
If an algorithm utilized in conjunction with these technologies to find a backup path cannot find a LFA backup path from the source node to the destination node (e.g., via the process defined in RFC 5286, then an alternative process can be utilized a way to find a remote-LFA (e.g., via IETF draft Remote LFA FRR, published Nov. 22, 2013). However, the process of pre-provisioning these backup paths and in particular the remote LFA backup paths is compute and resource intensive. Reducing the compute resources required reduces the cost of the requisite networking equipment and reduces downtime from possible network failures.